U.S. patent application number 09/874015 was filed with the patent office on 2002-03-07 for intraocular lens.
This patent application is currently assigned to Benz Research and Development Corporation, Benz Research and Development Corporation. Invention is credited to Benz, Patrick H., Ors, Jose A..
Application Number | 20020027302 09/874015 |
Document ID | / |
Family ID | 22097302 |
Filed Date | 2002-03-07 |
United States Patent
Application |
20020027302 |
Kind Code |
A1 |
Benz, Patrick H. ; et
al. |
March 7, 2002 |
Intraocular lens
Abstract
A one-piece intraocular lens formed from a copolymer of a
hydrophilic monomer and an alkoxy-alkylmethacrylate. The
intraocular lens is foldable so as to be insertable through a small
incision in the eye.
Inventors: |
Benz, Patrick H.; (Sarasota,
FL) ; Ors, Jose A.; (Sarasota, FL) |
Correspondence
Address: |
George C. Beck
FOLEY & LARDNER
Washington Harbour
3000 K Street, N.W., Suite 500
Washington
DC
20007-5109
US
|
Assignee: |
Benz Research and Development
Corporation
|
Family ID: |
22097302 |
Appl. No.: |
09/874015 |
Filed: |
June 6, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09874015 |
Jun 6, 2001 |
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09070771 |
May 1, 1998 |
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6267784 |
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Current U.S.
Class: |
264/1.38 ;
264/2.6; 264/2.7 |
Current CPC
Class: |
Y10S 623/926 20130101;
A61L 2430/16 20130101; C08L 33/12 20130101; G02B 1/043 20130101;
A61F 2/1616 20130101; A61L 27/16 20130101; Y10S 623/901 20130101;
A61F 2/16 20130101; A61L 27/16 20130101; A61L 27/52 20130101; A61F
2/16 20130101; C08L 33/14 20130101; G02B 1/043 20130101; C08L 33/14
20130101; A61L 27/16 20130101; C08L 33/14 20130101 |
Class at
Publication: |
264/1.38 ;
264/2.6; 264/2.7 |
International
Class: |
B29D 011/00 |
Claims
What is claimed is
22. (New) A method of forming a one-piece intraocular lens,
comprising: (a) polymerizing a mixture comprising a hydrophilic
monomer, an alkoxyalkyl methacrylate monomer, and a crosslinking
monomer to form a copolymer comprising an incorporated hydrophilic
monomer, an incorporated alkoxyalkyl methacrylate monomer, and at
least 0.25 percent by weight of an incorporated crosslinking
monomer based on the total weight of the dry copolymer; (b) forming
the copolymer into the one-piece intraocular lens, wherein the
one-piece intraocular lens comprises a haptic portion and an optic
portion formed from the copolymer and the hydrated copolymer has an
equilibrium water content of from 38 percent to about 10 percent by
weight based on the total weight of the hydrated copolymer.
23. (New) The method of forming a one-piece intraocular lens
according to claim 22, wherein the hydrophilic monomer comprises a
monomer of the formula HO-R.sub.1-MA and the alkoxyalkyl
methacrylate monomer comprises a monomer of the formula
R.sub.2-O-R.sub.3-MA, wherein R.sub.1, R.sub.2, and R.sub.3 are
independently selected from alkyl groups having 1 to 6 carbon atoms
and MA is methacrylate.
24. (New) The method of forming a one-piece intraocular lens
according to claim 23, wherein the copolymer consists essentially
of incorporated monomers of the formula R.sub.2-O-R.sub.3-MA and
the formula HO-R.sub.1-MA, and the incorporated crosslinking
monomer.
25. (New) The method of forming a one-piece intraocular lens
according to claim 23, wherein R.sub.1, R.sub.2, and R.sub.3 are
independently selected from alkyl groups having 1 to 4 carbon
atoms.
26. (New) The method of forming a one-piece intraocular lens
according to claim 22, wherein the one-piece intraocular lens is
foldable.
27. (New) The method of forming a one-piece intraocular lens
according to claim 22, wherein the copolymer has a refractive index
of greater than about 1.4.
28. (New) The method of forming a one-piece intraocular lens
according to claim 22, wherein the hydrophilic monomer comprises
hydroxyethyl methacrylate or hydroxypropyl methacrylate.
29. (New) The method of forming a one-piece intraocular lens
according to claim 22, wherein the alkoxyalkyl methacrylate monomer
comprises one or more monomer selected from the group consisting of
ethoxyethyl methacrylate, methoxyethyl methacrylate, propoxyethyl
methacrylate, and butoxyethyl methacrylate.
30. (New) The method of forming a one-piece intraocular lens
according to claim 22, wherein the copolymer comprises about 40 to
about 95 percent by weight based on the total weight of the dry
copolymer of the hydrophilic monomer, and about 5 to about 60
percent by weight of the alkoxyalkyl methacrylate monomer, based on
the total weight of the dry copolymer.
31. (New) The method of forming a one-piece intraocular lens
according to claim 22, wherein the copolymer comprises about 50 to
about 80 percent by weight based on the total weight of the dry
copolymer of the hydrophilic monomer and about 20 to about 50
percent by weight of the alkoxyalkyl methacrylate monomer, based on
the total weight of the dry copolymer.
32. (New) The method of forming a one-piece intraocular lens
according to claim 22, wherein the crosslinking monomer is ethylene
glycol dimethacrylate.
33. (New) The method of forming a one-piece intraocular lens
according to claim 22, wherein the mixture comprising the
hydrophilic monomer, the alkoxyalkyl methacrylate monomer, and the
crosslinking monomer further comprises a UV-monomer.
34. (New) The method of forming a one-piece intraocular lens
according to claim 22, further comprising (c) hydrating the
copolymer to form a hydrated copolymer.
35. (New) The method of forming a one-piece intraocular lens
according to claim 22, wherein the hydrated copolymer has an
equilibrium water content of from 18 to 32 percent by weight based
on the total weight of the hydrated copolymer.
36. (New) The method of forming a one-piece intraocular lens
according to claim 22, wherein the total weight of the hydrophilic
and the alkoxyalkyl methacrylate monomer in the copolymer is at
least 90 percent by weight based on the total weight of the dry
copolymer.
37. (New) The method of forming a one-piece intraocular lens
according to claim 22, wherein the total weight of the hydrophilic
monomer and the alkoxyalkyl methacrylate monomer in the copolymer
is at least 95 percent by weight based on the total weight of the
dry copolymer.
38. (New) The method of forming a one-piece intraocular lens
according to claim 22, wherein the mixture comprising the
hydrophilic monomer, the alkoxyalkyl methacrylate monomer, and the
crosslinking monomer further comprises a polymerization
initiator.
39. (New) The method of forming a one-piece intraocular lens
according to claim 22, wherein the mixture comprising the
hydrophilic monomer, the alkoxyalkyl methacrylate monomer, and the
crosslinking monomer is polymerized in a tubular or cylindrical
mold.
40. (New) The method of forming a one-piece intraocular lens
according to claim 22, wherein the mixture comprising the
hydrophilic monomer, the alkoxyalkyl methacrylate monomer, and the
crosslinking monomer is polymerized into a polymer rod comprising
the copolymer.
41. (New) The method of forming a one-piece intraocular lens
according to claim 40, wherein the method further comprises forming
a polymer blank or a polymer disc from the polymer rod and forming
the intraocular lens from the polymer blank or the polymer
disc.
42. (New) A method of forming a one-piece intraocular lens,
comprising: (a) polymerizing a mixture comprising a hydrophilic
monomer, an alkoxyalkyl methacrylate monomer, and a crosslinking
monomer to form a copolymer comprising an incorporated hydrophilic
monomer, an incorporated alkoxyalkyl methacrylate monomer, and an
incorporated crosslinking monomer; (b) forming the copolymer into
the one-piece intraocular lens, wherein the one-piece intraocular
lens comprises a haptic portion and an optic portion formed from
the copolymer, and further wherein the copolymer comprises about 40
to about 95 percent by weight of the hydrophilic monomer based on
the total weight of the dry copolymer, about 5 to about 60 percent
by weight of the alkoxyalkyl methacrylate monomer based on the
total weight of the dry copolymer, and at least 0.25 percent of the
crosslinking monomer based on the total weight of the dry
copolymer.
43. (New) The method of forming a one-piece intraocular lens
according to claim 42, wherein the hydrophilic monomer is of the
formula HO-R.sub.1-MA and the alkoxyalkyl methacrylate monomer is
of the formula R.sub.2-O-R.sub.3-MA, wherein R.sub.1, R.sub.2, and
R.sub.3 are independently selected from alkyl groups having 1 to 6
carbon atoms, and MA is methacrylate.
44. (New) The method of forming a one-piece intraocular lens
according to claim 42, wherein the crosslinking monomer is ethylene
glycol dimethacrylate.
45. (New) The method of forming a one-piece intraocular lens
according to claim 42, wherein the mixture comprising the
hydrophilic monomer, the alkoxyalkyl methacrylate monomer, and the
crosslinking monomer further comprises a polymerization
initiator.
46. (New) The method of forming a one-piece intraocular lens
according to claim 42, wherein the mixture comprising the
hydrophilic monomer, the alkoxyalkyl methacrylate monomer, and the
crosslinking monomer is polymerized in a tubular or cylindrical
mold.
47. (New) The method of forming a one-piece intraocular lens
according to claim 42, wherein the mixture comprising the
hydrophilic monomer, the alkoxyalkyl methacrylate monomer, and the
crosslinking monomer is polymerized into a polymer rod comprising
the copolymer.
48. (New) The method of forming a one-piece intraocular lens
according to claim 47, wherein the method further comprises forming
a polymer blank or a polymer disc from the polymer rod and forming
the intraocular lens from the polymer blank or the polymer disc.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Ser. No.
09/070,771 filed May 1, 1998, pending.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to intraocular lenses. The invention
also relates to methods of making such lenses, and to copolymers
useful, for example, in intraocular lenses.
[0004] 2. Description of Related Art
[0005] Various types of intraocular lenses (IOLs) are known. For
example, there are known one-piece IOLs and composite IOL having
multiple pieces. A one-piece IOL is one where both optic and
non-optic portions are made from one material. The non-optic
portions are referred to as haptic portions, and are used for
attachment purposes. Two general designs for the haptics are a
"plate-type" and a "C-haptic" type, both of which have a variety of
shapes. A plate design is shown in FIGS. 1A and 1B. A "C" design is
shown in FIGS. 2A and 2B. These Figures are discussed in more
detail below.
[0006] It is desired to reduce the length of incision needed to
insert the IOL into the eye. Reducing the length of the incision
requires the use of a very soft material for the lens; soft enough
to permit the lens to be folded, inserted through the incision, and
released. Thus, intraocular lenses are preferably foldable so that
they can be easily inserted into the eye. Approaches to achieve
foldable materials include use of lenses formed of hydrophobic
silicone-polymers, certain hydrophilic 2-HEMA homopolymers, and
composites of a hydrophilic optical core with hydrophobic
poly(methyl)methacrylate (p-MMA) based haptics.
[0007] IOLs with mechanically-attached haptics are lenses where the
optic-portion and the haptic-portion are made separately, usually
from different materials, and attached. For example, the lens
portion can be made of a hydrogel or silicone-based material and
the C-shape haptics from a rigid material like p-MMA. The p-MMA
haptics are attached to holes drilled into the optic portion.
[0008] Although P-MMA is the traditional hydrophobic IOL it is not
easily foldable and requires a relatively large incision for
insertion. To make hydrophobic materials foldable, there has been
included rubber-like materials, such as silicone derivatives, into
the rigid polymer matrix or use of materials consisting primarily
of silicone derivatives. Although the softness of a primarily
silicone material is ideal for folding prior to insertion, when the
lens and its haptics unfold in the eye, the almost gel-like
softness of the lens makes it difficult for a surgeon to properly
position the lens in the eye. Furthermore, the silicone lens often
does not provide sufficient rigidity for the lens after insertion
and the combination of deformation from compressive forces along
with lens movement can produce lens distortion and compromise the
optical integrity of the lens.
[0009] Because of its inherent properties, p-hydroxyethyl
methacrylate (a homopolymer of HEMA) has been used as a foldable
material for IOLs. However, the low refractive index of p-HEMA when
hydrated leads to limitations in the optical center design and a
compromise between its folding ability and its optical
requirements.
[0010] One of the limitations of one-piece P-HEMA hydrogel lenses
has been that the haptic portion lacks the desired dimensional
stability and can compromise lens positioning. To address this
issue, polymer materials have been combined to give a soft,
foldable intraocular composite lens such as P-HEMA or other soft
acrylic material for the optic zone, and a rigid structure around
the outside of the lens, made from a hard plastic such as P-MMA.
See U.S. Pat. No. 4,718,906 and U.S. Pat. No. 5,326,506, both
hereby incorporated by reference in their entireties, which
describe composite IOLs. These multicomponent materials are made by
embedding one material in the other, or by concurrent extrusion
processes, or by solidifying the hard material about the soft
material, or by forming an interpenetrating network of the rigid
component into a preformed hydrophilic core.
[0011] U.S. Pat. No. 5,326,506, discloses a composite intraocular
lens including a soft, pliable inner lens optic using rigid
haptics. The lens optic material is a low water content material
such as a copolymer of 2-HEMA and hydroxy hexylmethacrylate which
has a high refractive index due to its low water content. The hard
yet foldable P-MMA haptics, are formed by an interpenetrating
network.
[0012] An article by Chirila et al., J. Cataract Refract. Surf.,
pp. 154-162, Vol. 17, March 1991 discusses the toxicity effects of
residual monomers, such as 2-hydroxyethyl methacrylate, methyl
methacrylate, and 2-ethoxyethyl methacrylate, in IOLs. One piece
IOLs are not proposed.
[0013] U.S. Pat. No. 4,764,169, hereby incorporated by reference in
its entirety, discloses a composite intraocular lens including a
small, hard inner lens optic and a soft, pliable skirt surrounding
the lens optic. The lens optic material is a relatively hard
material such as P-MMA, polysulfone, or polycarbonate. The soft,
pliable skirt is a silicone, hydrogel or like material.
SUMMARY OF THE INVENTION
[0014] It is an object of the present invention to provide a
one-piece IOL that overcomes the disadvantages of known one-piece
IOLs and composite IOLs.
[0015] It is an object of the invention to provide an intraocular
lens that is foldable so as to be insertable through a small
incision in the eye.
[0016] It is also an object of the present invention to provide a
one-piece, intraocular lens having a soft, foldable optic portion
and haptic portion, wherein the optic and haptic portions are made
from the same soft hydrogel material, that protects the eye tissue
at the point of contact without sacrificing the lens positioning
properties.
[0017] It is also an object of the invention to provide a one-piece
intraocular lens having a soft, foldable optic portion and haptic
portion that has excellent biocompatibility with the patient's
eye.
[0018] It is also an object of the invention to provide a material
useful in both the optic and haptic portions of the IOL.
[0019] In accordance with these and other objectives there has been
provided in accordance with the present invention a one-piece
intraocular lens formed from a copolymer of a hydrophilic monomer
and an alkoxyalkyl methacrylate.
[0020] In accordance with these objectives, there is also provided
a one-piece intraocular lens, wherein both the optic and haptic
portions are formed from a copolymer of a monomer of formula
HO-R.sub.1-MA and a monomer of formula R.sub.2-O-R.sub.3-MA,
wherein R.sub.1, R.sub.2, and R.sub.3 are independently selected
from alkyl groups having 1 to 6 carbon atoms, and where MA is
methacrylate.
[0021] In accordance with the invention, there is also provided an
intraocular lens including a haptic portion and an optic portion,
wherein the haptic and optic portion are formed of the same or
different copolymer of a hydrophilic monomer and an alkoxyalkyl
methacrylate.
[0022] In accordance with the invention, there is also provided a
hydrogel copolymer of a hydrophilic monomer and an alkoxyalkyl
methacrylate, wherein the hydrophilic monomer is of formula
HO-R.sub.1-MA and the alkoxyalkyl methacrylate is of formula
R.sub.2-O-R.sub.3-MA, wherein R.sub.1, R.sub.2, and R.sub.3 are
independently selected from alkyl groups having 1 to 6 carbon
atoms, where MA is methacrylate, and wherein the hydrogel has a
water content of from about 10 to about 38 percent by weight, based
on the weight of the copolymer.
[0023] Further objects, features, and advantages of the present
invention will become apparent from the detailed description of
preferred embodiments that follows.
BRIEF DESCRIPTION OF THE FIGURES
[0024] FIG. 1A is a top view of an intraocular lens having a
plate-shaped haptic.
[0025] FIG. 1B is a side view of the intraocular lens having a
plate-shaped haptic shown in FIG. 1A.
[0026] FIG. 2A is a top view of an intraocular lens having a
C-shaped haptic.
[0027] FIG. 2B is a side view of the intraocular lens having a
C-shaped haptic shown in FIG. 2A.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0028] The intraocular lens of the present invention is a one-piece
lens having a soft, foldable central optic region and an outer
peripheral region (haptic-region). Both regions are made of a
copolymer of a hydrophilic monomer and an alkoxyalkyl methacrylate
monomer. Generally the optic and haptic are made of the same
copolymer. Unlike the composite materials described in the art,
wherein the optic and haptic regions are formed of different types
of polymers, in the present IOL, the optic and haptic regions are
formed of the same kind of copolymer; namely a copolymer of a
hydrophilic monomer and an alkoxyalkyl methacrylate. Preferably the
optic and haptic regions are formed from the same copolymer.
[0029] Both the central optic zone of the IOL and its haptics are
manufactured from a copolymer capable of being folded so that the
intraocular lens can be inserted through a small incision. The
haptic portion of the lens, although made from the same type of
copolymer as the optic portion, provides the required support for
the lens in the eye after insertion and unfolding of the lens and
tends to help stabilize the position of the lens after insertion
and the closure of the incision. The haptic portion design can be
any desired, for example, either a plate type or graduated
thickness spiral filaments, also known as a C-loop design.
[0030] FIGS. 1 and 2 illustrate examples of IOLs in accordance with
the present invention. figures are for illustrative purposes only
and do not limit the scope of the invention. For instance, the IOL
can be any type of IOL, so long as the IOL is a one-piece IOL
wherein the optic and haptic portions include the same type of
copolymer. In the figures, 1 is the optic portion of the lens, 2 is
the haptic portion, and 3 is a positioning hole. One skilled in the
art of IOLs understands the functions of these portions of the
IOL.
[0031] The optic portion 1 can be approximately 6 mm in diameter
prior to hydration. The 6 mm diameter is fairly standard in the
art, and is generally chosen to cover the pupil in its fully
dilated state under naturally occurring conditions. However, other
sizes are possible and the present invention is not limited to any
particular diameter or size of IOL. Furthermore, it is not
necessary that the lens optic portion be circular; it could also be
oval, square, or any other shape as is desired.
[0032] The intraocular lens comprises one or more non-optical
haptic components 2 extending away from the outermost peripheral
surface of the optic portion. The haptic components can be of any
desired shape, for example, graduated spiral filaments or flat
plate sections and are used to support the lens within the
posterior chamber of the eye. Lenses having any desired design
configuration can be fabricated. Further, although two types of
haptic designs are shown in the figures, the haptics can have
configurations other than those illustrated. Should the IOL include
other components besides the optical and haptic portions, such
other portions can be made of a copolymer as are the haptic and
optic portions, or if desired, another material.
[0033] The IOLs of the invention may be inserted into the eye in
known manners. For example, the IOL may be folded prior to
insertion into the eye by small, thin forceps of the type typically
used by ophthalmic surgeons. After the lens is in the targeted
location, it is released to unfold. The IOL of the present
invention is made of a physiologically inert soft polymeric
material that is capable of providing a clear, transparent,
refractive lens body even after folding and unfolding.
[0034] The optical and haptic portions of the IOL of the present
invention are formed from the same or different, preferably the
same, copolymer of a hydrophilic monomer and an alkoxyalkyl
methacrylate. The hydrophilic monomer can be selected from any
desired hydrophilic monomer known, for example, a monomer of
formula HO-R.sub.1-MA, wherein R.sub.1 is an alkyl group having 1
to 6 carbon atoms, preferably 1 to 4 carbon atoms. The alkoxyalkyl
methacrylate can be formed from any such monomers, for example, a
monomer of formula R.sub.2-O-R.sub.3-MA, wherein R.sub.2 and
R.sub.3 are independently selected from alkyl groups having 1 to 6
carbon atoms, preferably 1 to 4 carbon atoms. The copolymer
preferably contains at least about 90 weight percent, preferably at
least about 95 weight percent based on the total weight of the
copolymer, of the total of the hydrophilic monomer(s) and the
alkoxy-alkyl methacrylate(s).
[0035] The amount of the hydrophilic monomer and the
alkoxy-alkylmethacrylate monomers in the copolymer, can be varied
within a wide range to give the desired characteristics to the IOL.
Generally the amount of hydrophilic monomer is about 40 to about 95
percent by weight, preferably about 50 to about 90 percent, more
preferably about 60 to about 80 percent based on the total weight
of the copolymer. Examples of useful hydrophilic monomers include
hydroxyethyl methacrylate (HEMA=HO-R.sub.1-MA where R.sub.1 is
ethyl) and hydroxypropyl methacrylate (HPMA=HO-R.sub.1-MA where
R.sub.1 is propyl).
[0036] The alkoxyalkyl methacrylate monomers generally comprise
from about 5 to about 60 percent, preferably about 10 to about 50
percent, more preferably about 20 to about 40 percent, of the
copolymers. Examples of monomers useful as the alkoxyalkyl
methacrylate include ethoxyethyl methacrylate
(EOEMA=R.sub.2-O-R.sub.3-MA where R.sub.2 and R.sub.3 are ethyl),
methoxyethyl methacrylate (MOEMA=R.sub.2-O-R.sub.3-MA where R.sub.2
is methyl and R.sub.3 is ethyl), propoxyethyl methacrylate
(n-POEMA=R.sub.2-O-R.sub.3-MA where R.sub.2 is-propyl and R.sub.3
is ethyl), and butoxyethyl methacrylate
(n-BuOEMA=R.sub.2-O-R.sub.3-MA where R.sub.2 =n-butyl and R.sub.3
=ethyl).
[0037] The copolymers can be prepared using conventional
polymerization techniques known to those in the field of polymer
chemistry. Crosslinkers can be added during polymerization as known
in the art. For example, any crosslinking or difunctional monomer
used in the art such as ethylene glycol dimethacrylate (EGDMA), can
be used in effective amounts to give the desired crosslinking, for
example, in a concentration range of 0 to about 10 percent, such as
about 0.01 to about 0.4 percent by weight, based on the weight of
the polymer.
[0038] Also, if desired an initiator can be used in the
polymerization. Any initiator commonly used in the art, such as azo
derivatives, like 2,2-azobis (2,4-dimethylvaleronitrile) and
propanenitrile,2-methyl,2,2'-a- zobis, can be used. The initiator
is used in an amount effective for initiation purposes, and is
generally present from about 0.01 to 1.0% by weight, based on the
weight of the copolymer.
[0039] The copolymer used in the present invention can include in
addition to a hydrophilic monomer and an alkoxyalkyl methacrylate,
additional monomers, such as additional hydrophilic monomers or
acrylates, as well as monomers that impart UV absorption to the
copolymer. Any monomer copolymerizable with the hydrophilic monomer
and the alkoxyalkyl methacrylate monomers can optionally be used,
so long as such does not materially, adversely effect the basic
characteristics of the IOL. Examples of useful additional monomers
that can used are described in U.S. Pat. No. 5,326,506, hereby
incorporated by reference, directed to a composite IOL. In
particular, the monomers indicated as copolymerizable with the HEMA
in the '506 patent, for the optic portions of the patent's IOL
lens, can be used as optional additional monomers in the copolymers
of the present invention. Such optional additional monomers,
preferably are present in a total amount of not more than 10 weight
percent, generally less than 5 weight percent, based on the total
weight of the copolymer. Thus, the term copolymer for the purposes
of this application means that the polymer is formed from 2 or more
different polymerizable monomers.
[0040] As mentioned above, it may be useful to add crosslinking
agents such as ethylene glycol dimethacrylate (EGDMA), for example,
to enhance the resulting copolymer's dimensional stability. It may
also be advantageous to add ultraviolet (UV) absorbing compounds
with the lens monomers prior to polymerization for incorporation
into the resultant polymer, as is known in the art. The UV absorber
should preferably be capable of polymerization into the lens matrix
so as to resist extraction under physiologic conditions. The
UV-absorbing monomer can be present in an amount effective to give
the desired UV-absorbing properties, generally less than 4 percent
by weight of the copolymer, such as from 0.01 to about 1 percent by
weight of the copolymer.
[0041] Table 1 below summarizes exemplary constituents useful in
making the copolymer for the IOLs of the present invention.
1TABLE 1 Concen- tration HO-R.sub.1-MA Range R.sub.2-O-R.sub.3MA
Concentration R.sub.1 = Ethyl (Wt. %) R.sub.2 = R.sub.3 = Range
(Wt. %) HEMA 40 to 95 Ethyl, Ethyl, or 5 to 60 Methyl, n- Propyl
Propyl, i-Propyl, n-Butyl, i-Butyl, or sec-Butyl HO-R.sub.1-MA
R.sub.2-O-R.sub.3-MA R.sub.1 = Propyl R.sub.2 = R.sub.3= HPMA 40 to
95 Ethyl, Ethyl, or 5 to 60 Methyl, n- Propyl Propyl, i-Propyl,
n-Butyl, or i-Butyl
[0042] Examples of specific copolymers useful in the present
invention are shown below in Table 2.
2TABLE 2 General R.sub.2-O-R.sub.3-MA General HO-R.sub.1-MA Range
R.sub.3 = Ethyl R.sub.3 = Propyl Range HEMA 40 to 95 EOEMA EOPMA 5
to 60 HPMA MeOEMA MeOPMA n-PrOEMA n-PrOPMA i-PrOEMA i-PrOPMA
n-BuOEMA n-BuOPMA i-BuOEMA i-BuOPMA sec-BuOEMA sec-BuOPMA
[0043] The copolymers used in the IOLs preferably have a refractive
index (RI) of greater than about 1.4 generally from about 1.4 to
about 1.5. This is significantly greater than the RI of p-HEMA. An
advantage of hydrogel copolymers of the present invention is that
they can be folded prior to insertion, thereby reducing the size of
the incision. Generally, the RI value for a hydrogel decreases
progressively with increasing water content. The RI value of a
material influences the design and the parameters of an IOL. Hence,
besides biocompatibility, an ideal IOL would be foldable, have the
ability to quickly regain its shape and optical quality after
insertion, and have a high RI value. The IOLs of the present
invention have been found to have these desired characteristics.
That is, the IOLs of the present invention fulfill the requirements
of a high performance intraocular lens and have excellent folding
characteristics, relatively high refraction index, and excellent
unfolding characteristics.
[0044] A preferred material for both the optical and haptic regions
of the IOL is a copolymer of 2-hydroxyethyl methacrylate (2-HEMA)
and ethoxyethyl methacrylate (EOEMA).
[0045] The hydrogels of the copolymers have a low water content,
generally from about 10 to about 38 percent, preferably about 18 to
32 percent by weight, based on the total weight of the copolymer.
The IOLs of the present invention may be formed by methods known in
the art. For example, in an exemplary process first the monomers
that form the copolymer are polymerized into a polymer rod; polymer
blanks or discs are formed from the rod, and then the blanks are
cut, for example, by a lathe into the intraocular lens. The rods
can be made by a procedure which begins with polymerizing in a
tubular or cylindrical mold a liquid mixture of initiator and
co-monomers such as 2-HEMA and EOEMA, to form an optically clear
soft lens body. As discussed above, it may be desirable to
incorporate cross-linking materials and ultraviolet-absorbing
compounds during polymerization or into the resultant polymer
matrix. The polymer rods are then cut and centerless ground, into
blanks of the desired diameter and thickness by lathe cutting and
machine milled in the conventional manner into an intraocular
lens.
[0046] Generally, the composite material rod is lathe cut or ground
to a diameter 0.5 to 2.0 mm thicker than the required distance from
the center of the lens body to the furthest edge of the legs or
haptics. This rod is then sawed or otherwise cut into blanks of
uniform thickness. The blanks are then heat treated and ground and
lapped to a diameter and thickness suitable for lathe cutting and
machine milling in the conventional manner into the intraocular
lens of the present invention.
[0047] A general description of a stepwise process for forming the
blanks into IOLs is set forth in the flow chart below. One having
ordinary skill in the field of IOL manufacturing, from a review of
the present specification, can make IOLs using the general
knowledge in the art on IOL manufacture. 1
[0048] The invention also relates to a hydrogel copolymer of a
hydrophilic monomer and an alkoxyalkyl methacrylate, wherein the
hydrophilic monomer is of formula HO-R.sub.1-MA and the alkoxyalkyl
methacrylate is of formula R.sub.2-O-R.sub.3-MA, wherein R.sub.1,
R.sub.2, and R.sub.3 are independently selected from alkyl groups
having 1 to 6 carbon atoms, wherein the hydrogel has a water
content of from about 10 to about 38 percent by weight, based on
the weight of the copolymer. The hydrophilic and alkoxyalkyl
methacrylate monomers can be selected from those mentioned above,
and the copolymer can include the proportion of monomers and
optional other monomers discussed above. The copolymer can be
formed as discussed above.
[0049] These copolymers can be used in numerous applications, such
as in contact lenses, as the optical portion of IOLs, as the haptic
portion of an IOL, and as discussed above, as both the optical and
haptic portion of the IOL.
[0050] The invention is illustrated by the following examples. The
examples only illustrate the invention, and do not limit it.
EXAMPLE I
Preparation of HEMA/EOEMA Copolymer with 18% Water Content
[0051] 548.3 grams of 2-HEMA were mixed with 446.1 grams of EOEMA
and 0.7 grams of 2,2-azobis (2,4-dimethylvaleronitrile) were added.
The total diester concentration was adjusted to 0.3% by weight with
ethylene glycol dimethacrylate (EGDMA). The mixture was degassed
while applying vigorous stirring. The mixture was dispensed into
cylindrical molds, polymerized at 30.degree. C. for 10 hours, and
post-cured at 100.degree. C. for 5 hours. The polymer was then
removed from the molds and formed into contact lens blanks. The
mechanical formation process comprised cutting the polymer into
cylinders of 0.5 to 0.65 inches (1.27 to 1.65 cm.) in diameter and
0.1 to 0.2 inches (0.25 to 0.51 cm.) in thickness. The blanks were
further cured at 100.degree. C. for 5 hours. After curing, the
blanks were ground and lapped to right cylinder with the desired
dimensions.
EXAMPLE II
Preparation of HEMA/EOEMA Copolymer with 25% Water Content
[0052] 707.8 grams of 2-HEMA were mixed with 287.0 grams of EOEMA
and 0.7 grams of 2,2-azobis (2,4-dimethylvaleronitrile) were added.
The total diester concentration was adjusted to 0.3% by eight with
ethylene glycol dimethacrylate (EGDMA). The mixture was degassed
while applying vigorous stirring. The mixture was dispensed into
cylindrical molds, polymerized at 30.degree. C. for 10 hours, and
post-cured at 100.degree. C. for 5 hours. The polymer was then
removed from the molds and formed into contact lens blanks. The
mechanical formation process comprised cutting the polymer into
cylinders of 0.5 to 0.65 inches (1.27 to 1.65 cm.) in diameter and
0.1 to 0.2 inches (0.25 to 0.51 cm.) in thickness). The blanks were
further cured at 100.degree. C. for 5 hours. After curing, the
blanks were ground and lapped to right cylinder with the desired
dimensions.
EXAMPLE III
Preparation of HEMA/EOEMA Copolymer with 24% Water Content and
UV-Protection
[0053] 1770.4 grams of 2-HEMA were mixed with 717.6 grams of EOEMA,
12.5 grams of methacryloxy siloxane-2-hydroxy benzophenone and 1.75
grams of 2,2-azobis (2,4-dimethylvaleronitrile) were added. The
total diester concentration was adjusted to 0.25% by weight with
ethylene glycol dimethacrylate (EGDMA). The mixture was degassed
while applying vigorous stirring. The mixture was dispensed into
cylindrical molds, polymerized at 30.degree. C. for 10 hours, and
post-cured at 100.degree. C. for 5 hours. The polymer was then
removed from the molds and formed into contact lens blanks. The
mechanical formation process included cutting the polymer into
cylinders of 0.5 to 0.65 inches (1.27 to 1.65 cm.) in diameter and
0.1 to 0.2 inches (0.25 to 0.51 cm.) in thickness. The blanks were
further cured at 100.degree. C. for 5 hours. After curing, the
blanks were ground and lapped to right cylinder with the desired
dimensions.
EXAMPLE IV
Preparation of HEMA/EOEMA Copolymer with 28% Water Content
[0054] 763.1 grams of 2-HEMA were mixed with 231.9 grams of EOEMA
and 0.7 grams of 2,2-azobis (2,4-dimethylvaleronitrile) were added.
The total diester concentration was adjusted to 0.3% by eight with
ethylene glycol dimethacrylate (EGDMA). The mixture was degassed
while applying vigorous stirring. The mixture was dispensed into
cylindrical molds, polymerized at 30.degree. C. for 10 hours, and
post-cured at 100.degree. C. for 5 hours. The polymer was then
removed from the molds and formed into contact lens blanks. The
mechanical formation process comprises cutting the polymer into
cylinders of 0.5 to 0.65 inches (1.27 to 1.65 cm.) in diameter and
0.1 to 0.2 inches (0.25 to 0.51 cm.) in thickness. The blanks were
further cured at 100.degree. C. for 5 hours. After curing, the
blanks were ground and lapped into right cylinder with the desired
dimensions.
[0055] The blanks formed in the above examples can be formed into
one piece IOLs using conventional techniques well known to those in
the art. Preferably, but not necessarily, both the optic and haptic
portions are formed of the same copolymer.
[0056] The formulations of the Examples are summarized in Table 3
below.
3 TABLE 3 EXAM- EXAM- EXAM- EXAM- PLE 1 PLE 2 PLE 3 PLE 4 (Wt. in
(Wt. in (Wt. in (Wt. in Component grams) grams) grams) grams)
2-HEMA 548.2 707.8 1770.4 763.1 EOEMA 446.1 287.0 717.6 231.9 EGDMA
2.5 2, 5 6.3 2.5 2,2-azobis . . . 0.7 0.7 1.75 0.7 UV-Monomer -- --
12.5 --
[0057] The properties of the example formulations are shown in
Table 4 below.
4TABLE 4 EXAM- EXAM- EXAM- EXAM- PROPERTY PLE 1 PLE 2 PLE 3 PLE 4
Water Content (%) 18 25 24 28 Expansion Coefficient: not not
measured measured Linear 1.11 1.11 Radial 1.11 1.11 Refractive
Index: not measured Dry 1.4913 1.5011 1.495 Wet 1.4704 1.4597
1.4614 Hardness (Shore D) 81 86 86 not measured (1) Water content
and residuals are determined using a gravimetric method that
records the wet and dry weights of a number of sample discs through
2 hydration and drying cycles. (2) Expansion coefficients (radial
and linear) are determined by using fabrication lenses of a design
that yields even thickness lenses. Both linear and radial
dimensions of the lens are measured in the dry state, followed by
lens hydration and repeat of the linear and radial dimension
measurements. The coefficients are obtain from the ratios of wet
and dry. (3) Refractive Index is obtained on both dry and hydrated
buttons using an Abbe 3L Refractometer calibrated with
1-bromonaphthalene. (4) Shore D Hardness is obtained using a Shore
D durometer (Serial No. 9075) with a calibrated reference block
D34.
[0058] While several embodiments of the invention have been
described, it will be understood that it is capable of further
modifications, and this application is intended to cover any
variations, uses, or adaptations of the invention, following in
general the principles of the invention and including such
departures from the present disclosure as to come within knowledge
or customary practice in the art to which the invention pertains,
and as may be applied to the essential features hereinbefore set
forth and falling within the scope of the invention or the limits
of the appended claims.
* * * * *